Resource allocation for multi-cell OFDMA based cooperative relay network

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Resource Allocation for Multi-cell OFDMA

Based Cooperative Relay Network

Nidhal Odeh

A dissertation submitted in partial fulﬁlment of the requirements for the degree of

Doctor of Philosophy

University of Technology, Sydney

Faculty of Engineering and Information Technology Centre for Real-Time Information Networks

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Supervisor:

Associate Prof. Mehran Abolhasan

Co-supervisors: Dr. Daniel Franklin Prof. Farzad Safaei∗

University of Technology, Sydney

Faculty of Engineering and Information Technology

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STATEMENT OF ORIGIN

I certify that the work in this thesis has not previously been submitted for a degree nor has it been submitted as part of requirements for a degree except as fully acknowledged within the text.

I also certify that the thesis has been written by me. Any help that I have received in my research work and the preparation of the thesis itself has been acknowledged. In addition, I certify that all information sources and literature used are indicated in the thesis.

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Nidhal Odeh

Faculty of Engineering and Information Technology University of Technology, Sydney

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Abstract

Cooperative communications is emerging as an important area within the ﬁeld of wireless communication systems. The fundamental idea is that intermediary nodes, called relay stations (RSs), who are neither the data source nor destina-tion, are used to assist in communication between sender and receiver. In order to maximise their performance, networks which employ RSs require a new re-source allocation and optimisation technique, which takes the RSs into account as a new resource.

Several proposals have been presented for the purpose of optimising the dis-tribution of available resources between users. These proposals were developed based on various network scenarios and assumptions. In most cases, impracti-cal assumptions such as; inter-cell interference (ICI) free and full availability of channel state information (CSI) were considered. However, the need for more robust, fair and practical resource allocation algorithms motivated us to study the resource allocation algorithm for OFDMA based cooperative relay networks with more realistic assumptions.

This thesis focuses on the resource allocation for the uplink OFDMA based cooperative relay networks. Multiple cells were considered, each composed of a single base station (destination), multiple amplify and forward (AF) relay sta-tions and multiple subscriber stasta-tions (sources). The eﬀects of cell inter-ference (ICI) have been considered to optimise the subcarrier allocation with low complexity. The optimisation problem aims to maximise the sum rate of all sources while maintaining a satisfactory degree of fairness amongst them.

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assuming full and partial channel state information for the interference limited OFDMA-based cooperative relay network. In the proposed algorithm, relay se-lection is initially performed based on the level of ICI. Then, subcarrier allocation is performed on the basis of maximum achieved utility under the assumption of equal power allocation. Finally, based on the amount of ICI, a modiﬁed waterﬁll-ing power distribution algorithm is proposed and used to optimise the subcarrier power allocation across the allocated set of subcarriers.

This thesis also investigates the impact of the relay-to-destination channel gain on subcarrier allocation for uplink OFDMA based cooperative relay net-works using multiple amplify-and- forward (AF) relaying protocols. The closed form outage probability is derived for the system under partial channel state information (PCSI) and considering the presence of inter-cell interference (ICI).

The proposed resource allocation algorithms as well as the mathematical anal-ysis were validated through computer simulations and the results were presented for each chapter. The results show that, compared to conventional algorithms, the proposed algorithms signiﬁcantly improve system performance in terms of total sum data rate, outage probability, complexity and fairness.

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ACKNOWLEDGMENTS

This work would not been accomplished without the help of so many people. In the following lines is a brief account of some but not all who deserve my thanks.

First, I would like to thank Associate Professor Mehran Abolhasan for pro-viding the opportunity to be one of his postgraduate students at the ﬁrst place, and for taking the burden of supervising this research. He supported, helped, reviewed and motivated this research.

My deepest gratitude and appreciation also goes to Dr. Daniel R. Franklin and Professor Farzad Safaei for their valuable comments and suggestions which have been indispensable in the preparation of this thesis.

I also would like to thank the Australian Research Council (ARC), the Fac-ulty of Engineering and Information Technology and the graduate school, UTS for the grant and ﬁnancial support to which allows me to accomplish this work.

I am very grateful to Mr. John Hazelton for proofreading my thesis and pro-viding me with useful comments and suggestions.

I owe many thanks and appreciation all my current and erstwhile colleagues and friends. I learned something new from each one of you, and for that i am very grateful.

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Thank you to my parents, Ahmed and Asmahan, for their unconditional sup-port and allowing me to be as ambitious as I wanted. It was under their watchful eye that I gained so much drive and an ability to tackle challenges head on. And thank you to my siblings and relatives for your encouragements and support.

Finally, and most importantly, I would like to thank my wife Shaden and my two little girls, Leanne and Sama, who missed out on a lot of Daddy time while I sought intellectual enlightenment. Their support, motivations and quiet patience were undeniably the bedrock upon which the past few years of my life have been built.

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LIST OF FIGURES

Figure Number Page

1.1 Multi-cell cooperative relay network . . . 3

1.2 Resource allocation for OFDMA possible scinarios . . . 4

2.1 Evolutions of mobile communication systems . . . 10

2.2 Multiple Access Techniques (MAT) . . . 14

2.3 Orthogonal subcarriers in OFDM system . . . 16

2.4 Orthogonal Frequency Division Multiple Access (OFDMA) . . . . 17

2.5 Cooperative relay network model . . . 19

2.6 Coverage extension using relay station . . . 20

4.1 Multi-cell cooperative relay system model . . . 55

4.2 Total achieved sum rate of the proposed algorithm compared to conventional algorithm with K=256 and R=6 . . . 66

4.3 The rate reduction ratio when adopting the proposed algorithm compared to the conventional one for SNR=20 dB, K=256 and R=6 67 4.4 Total network sum rate, K=256, S=40, 2 cells each with 4 RSs . . 68

4.5 Total network sum rate with diﬀerent number of cells, K=256, S=40 and R=4 . . . 69

5.1 Multi-cell interference limited OFDMA-based cooperative relay system model . . . 73

5.2 Utility and detrimental functions . . . 75

5.3 ICI mitigation using the proposed ICI-based RS selection algorithm 80 5.4 ICI based water-ﬁlling algorithm . . . 85 5.5 Total sum data rate as a function of SNR; K = 256, I = 4, R = 4

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5.9 Total sum data rate as a function of SNR, K = 256, I = 4, R = 4 and S = 20 . . . 92 5.10 Total achieved sum rate of the proposed algorithm with Full

(esti-mation error ()=0.0) and partial (esti(esti-mation error ()=0.01 and 0.1) CSI, K=20, K=256 and R=4 . . . 93 6.1 Network setup example, S = 20, I = 10 and R = 4 . . . 101 6.2 Total network rate vs. number of ICI sources for the conventional

and proposed schemes, S = 25, K = 128 and R = 4 . . . 102 6.3 Outage probability vs. number of ICI sources for the conventional

and proposed schemes, S = 25, K = 128 and R = 4 . . . 103 6.4 Hamming distance between the allocation vectors based on the

conventional and proposed schemes, SS = 25, K = 128 and R = 4 104 6.5 Outage probability vs. number of users for diﬀerent number of

ICI, K = 128 and R = 4 . . . 105 6.6 Average execution time reduction using the proposed scheme over

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LIST OF ACRONYMS

1st _G _{First Generation}

2nd _G _{Second Generation}

3rd G Third Generation 4th _G _{Fourth Generation}

AF Amplify and Forward

AMPS Advance Mobile Phone Service AWGN Additive White Gaussian Noise BE Best Eﬀort

BPA Binary Power Allocation BS Base Station

BTS Base Transceiver Station BW Bandwidth

CDMA Code Division Multiple Access CF Compress and Forward

CSI Channel State Information CSMA Carrier Sense Multiple Access DF Decode and Forward

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GPRS General Packet Radio Service

GSM Global System for Mobile Communication HSDPA High-Speed Downlink Packet Access ICI Inter Cell Interference

ICI-RS ICI-based Relay Selection IFFT Inverse Fast Fourier transform LTE Long Term Evolution

MA Multiple Access

MAC Medium Access Control MAI Multiple Access Interference MIMO Multiple Input Multiple Output MMR Mobile Multi-hop Relay

MRC Maximum Ratio Combining MS Mobile Station

MUI Multiuser Interference NAK Negative Acknowledgement

OFDM Orthogonal Frequency Division Multiplexing OFDMA Orthogonal Frequency Division Multiple Access OSDMA Orthogonal Space Division Multiple Access PA Power Allocation

PCSI Partial Channel State Information PDF Probability Density Function PHY Physical

PSK Phase-shift Keying

PSTN Public Switched Telephone Network QAM Quadrature Amplitude Modulation QOS Quality of Service

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RC Rate Constraint RD Relay To Destination

RRM Radio Resource Management R-RS Random Relay Selection RS Relay Station

SCI Statistical Channel Information SDMA Space Division Multiple Access SER Symbol Error Rate

SINR Signal to Interference and Noise Ratio SMS Short Message Service

SNR Signal to Noise Ratio SR Source to Relay

TDD Time Division Duplexing TDMA Time Division Multiple Access

W-CDMA Wideband- Code Division Multiple Access WF Water-Filling

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LIST OF SYMBOLS

Pk _{Subcarrier’s Power}

P_T Total power

N Cχ2 Non-central Chi-square Distribution with Two Degrees of Freedom

k Estimation Error Γ(2(n + 1)) Gamma Function

γ(a, b) Incomplete Gamma Function

γ_a,b SNR Ratio Between a and b Channel ˆ

hk

a,b Estimated Channel Gain between a and b Nodes

Gs Urgency Factor ρ Allocation Index σ2 Variance 2F1 Hypergeometric Function D(.) Detrimental Function F I Fairness Index g_r RS Ampliﬁcation Factor hk

a,b Instantaneous Channel Gain between a and b

Nodes

I Interference

I₀ Zeroth-order Modiﬁed Bessel Function of the First Kind

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P_out Outage Probability

P_r Probability

R Data Rate

R_min Minimum Data Rate Requirements

R_T Total Data Rate

T_s Time Slot

U Utility Function

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Resource allocation for multi-cell OFDMA based cooperative relay network